1. Technical Field
The present invention is directed toward corrugators, and more particularly toward plastic tile corrugators.
2. Background Art
Due to the utility of corrugated plastic tiles, for example, as buried drainage conduits, there is a substantial need for devices which can continuously and efficiently mold lengths of corrugated plastic tiles.
Several such devices are shown, for example, in U.S. Pat. Nos. 4,165,214, 4,199,314, 4,439,130, 4,492,551, 4,718,844, and 5,059,109. These prior art devices provide varying degrees of efficiency and produce varying quality tiles.
However, generally speaking, each of these prior art devices include mold blocks which define half (180 degrees) of a generally tubular mold tunnel when mated together in a substantially straight molding section. These mold blocks are generally either carried about one continuous pathway and mated together in a clamshell type of arrangement along the molding section, or are carried about two continuous pathways with one side of each such pathway bringing the mold blocks together in mating relationship to similarly form a molding section. The mold blocks are separated at both the beginning and end of the molding section to allow introduction of extruded plastic for molding at the beginning of the molding section and to allow the mold blocks to be drawn clear of the molded tile at the end of the molding section.
Along the molding section of the above referenced prior art devices, extruded plastic is caused to conform to the mold tunnel. Since the mold tunnel is typically not uniform (that is, it is corrugated with grooves and lands along its length), it is important that this be properly accomplished, as by drawing a vacuum outside the extruded plastic, introducing a pressure within the extruded plastic, or some combination thereof where vacuum molding is done, passages have been provided within the mold blocks to allow the extruded plastic to be drawn to the mold tunnel about the inner periphery of the mold blocks.
Of course, as with any device, it is desirable to be able to operate at maximum efficiency, with a maximum output rate, in order to maximize the revenue realized from its use. That need is particularly true with these devices in view of the relatively high initial cost of the device and the related relatively high revenue requirements needed simply to recoup that initial cost. Because of the relatively low unit cost of the tiles produced by such devices, high quantities of manufactured tiles are needed to meet those revenue requirements. Those revenue requirements are further increased by the need for, and cost of, different sets of mold blocks for each different size of corrugated tile to be manufactured.
The present invention is directed toward overcoming one or more of the problems set forth above.